All we have to chalk this up to at the moment is Geithner's testimony, and more importantly the Q and A before congress this AM.  This has stocks shooting up drastically along with tsy yields.  MBS have tightened dramatically in the face of the treasury sell off but have been unable to avoid going negative on the day.

The 4.0 is down 6 ticks to 99-30

4.5 down 2 ticks to 101-28

5.0 down a tick to 103-00

Reprices for the worse are likely.